The present invention relates to methods and apparatus for recording information on magnetic disk storage media, and in particular, for efficiently defining disk tracks on same.
Rapid advances are being made in the density of magnetic recording i.e. the number of bits per square inch that can be recorded. Leading edge products currently store 10 billion bits per square inch and this is generally expected to increase 10 fold in the next 3 or 4 years. A typical disk drive storage system includes a spindle member that supports a circularly shaped magnetic recording medium (i.e., a disk), and a read/write head attached to a recording arm, for reading/writing information from or onto the disk. Information is recorded on the disk by altering the magnetization direction of small radial segments of the disk, wherein the segments are located in narrow annular tracks arranged concentrically. A read/write head positioned over the track can read or write an entire track with each revolution of the disk. Also recorded in each track on the disk are periodic segments that identify the track number, the segment number, and information that allows the deviation of the read head from the track center to be calculated and nulled. This information is put onto the disk immediately following the assembly operation using a xe2x80x9cservo-writerxe2x80x9d which typically monitors the position of the recording arm using a laser interferometer or a rotary encoder. However, this approach is very slow and will take greater amounts of time to complete as the track density increases on future systems. It is also subject to unrepeatable errors caused by fluttering or vibration of the disk while it is being servo-written. There is some question about the technical feasibility of extending present-day techniques to higher track densities because of the positional errors, which are generated by the departures of the disk from being perfectly flat, and disk vibrations.
Spatial Period Division (SPD) is a technique for producing a periodic or quasieriodic pattern of period xe2x80x9cp/mxe2x80x9d from a master pattern of period xe2x80x9cpxe2x80x9d (where xe2x80x9cmxe2x80x9d is an integer). SPD utilizes the near-field diffraction pattern of a grating. The phenomenon of SPD has been reported on previously and is the subject of an invention by Flanders and Smith, U.S. Pat. No. 4,360,586, which patent is incorporated by reference herein. SPD works best when used to xe2x80x9cdoublexe2x80x9d the spatial frequency of an existing grating.
The near field diffraction pattern of a grating can be described by a superposition of all the diffracted orders from the grating. By analyzing the diffracted orders, two observations can be made: First, at discrete distances (gaps) from the grating, the diffracted orders add in such a way as to produce harmonics of the original grating. In particular, a grating of period xe2x80x9cp/mxe2x80x9d is produced in the near field diffraction pattern of a grating of period xe2x80x9cpxe2x80x9d at a gap given by:
Gap=p2/(mxcex)
Second, when considering pure phase gratings with only the positive and negative first order terms (i.e., all non-first order terms are zero), the first-order diffracted orders overlap to produce a grating of period xe2x80x9cp/2xe2x80x9d for all gaps where the analysis is valid (typically gaps greater than a few wavelengths). Therefore, a reasonable way to produce gratings of period xe2x80x9cp/2xe2x80x9d is to fabricate phase gratings of period xe2x80x9cpxe2x80x9d with all non-first order diffraction terms equal to zero, and illuminate the grating at wavelength xcex.
U.S. Pat. No. 4,048,660 discloses an improved servo block pattern that bands a plurality of parallel record tracks into a track seek and follow band. Servo block positions in the record tracks, plus the longitudinal duration of the signal bursts enable simultaneous track seeking and following within a band of tracks. Servo apparatus operable with such patterns adapt to amplitude variations of the servo readback signal to reduce the effect of amplitude variations on servo performance. The servo blocks may have differing frequencies or correlation patterns for enhancing track seek and follow functions.
U.S. Pat. No. 5,572,392 discloses an arbitrary pattern write head assembly for writing timing-based servo patterns on magnetic storage media. The assembly comprises: (a) a first pole piece comprising a substrate comprising a magnetic material, the substrate having a major surface; (b) a plurality of electrically conducting windings formed on the major surface; and (c) a second pole piece formed on the substrate, with a portion thereof formed above the plurality of electrically conducting windings and electrically insulated therefrom, the second pole piece having at least one opening therethrough defining a gap above the electrically conducting windings and the substrate, the second pole piece comprising at least two layers, each layer comprising a magnetic material. A method of batch fabricating servo writer heads is also provided for batch fabrication of servo writer heads at a very low cost. The method enables fabrication of heads capable of azimuthal recording commonly practiced in the video recording art. Hard nitrided Fe/NiFe poletip materials are used to minimize wear in tape head use.
The present invention relates to methods and apparatus for recording information on magnetic disk storage media, and in particular, efficiently defining disk tracks on same.
A first aspect of the invention is a track-writing apparatus for forming tracks, with a track width, and track spaces, with a space width, on a magnetic media disk having an upper surface and comprising a magnetic medium with a thermal diffusion length. The apparatus comprises, in order along an optical axis: a laser light source capable of providing a pulsed beam of laser light; an illumination shaping optical system that provides substantially uniform illumination over an exposure region; and a phase plate having a phase grating with a grating period p. The phase plate is arranged proximate and substantially parallel to the upper surface of the disk so as to form a periodic irradiance distribution at the surface of the disk when the phase plate is illuminated with the exposure region. The irradiance distribution is capable of heating one or more regions of the disk to beyond the Curie temperature of the magnetic media.
A second aspect of the invention is a process for forming tracks in a magnetic disk having a periodic magnetic pattern formed therein. The process includes the steps of first, irradiating an angular segment of the disk with an irradiance distribution formed by spatial period division in the presence of a fixed magnetic field, and then rotating the disk underneath the pulsed irradiance distribution to form closed, concentric, annular magnetically uniform, i.e. blank spaces in the periodically magnetized medium. The blank spaces define closed annular tracks (i.e., serve to define the boundaries between the closed annular tracks). Each track comprises an annular portion of the periodically magnetized pattern.
A third aspect of the invention is a process for forming tracks in a magnetic disk. The process includes the steps of first, forming a periodic magnetic pattern in the disk, then irradiating an angular segment of the disk with an irradiance distribution formed by spatial period division and in the presence of a fixed magnetic field. Rotating the disk underneath the irradiance distribution forms closed concentric annular spaces with a fixed tangential magnetic orientation (which erases the original periodic magnetic orientation in the irradiated spaces on the disk) in the otherwise periodically magnetized medium, thereby defining closed annular tracks. Each track comprises an annular portion of the periodically varying magnetic pattern.
A fourth aspect of the invention includes a method of formatting a disk by performing the steps as described above in connection with the third aspect of the invention, and then formatting the disk by writing track identification information onto each track.
A fifth aspect of the invention is writing non-tracking information or data onto at least a portion of the formatted disk tracks formed according to the fourth aspect of the invention.
A sixth aspect of the invention is a magnetic media disk product having tracks formed using the process briefly described above and described in greater detail below.
A seventh aspect of the invention is a disk drive apparatus comprising a spindle member having a spindle axis, and a magnetic media disk according to the present invention arranged on the spindle member. The apparatus further includes a spindle member drive unit operatively connected to the spindle member for driving the spindle member about the spindle axis so as to rotate the disk about the spindle axis. Also included is a pivot arm having a distal end that extends over the disk, a proximate end pivotally mounted to a pivot arm axis, and an underside facing the disk. A writing head is arranged on the underside of the pivot arm at or near the distal end. Further included is a pivot arm control unit operatively connected to the pivot arm so at to move the pivot arm about the pivot axis so as to move the writing head over the disk.